To　enhance　the　accuracy,　a　new　method　for　analysizing　the　error　sensitivity　of　machine　tool　is　presented.　Beyond　the　consideration　of　a　particular　machine　tool,　a　general　methodology　is　presented　based　on　the　multi-body　kinematics　theory.　Regarding　a　machine　tool　as　a　rigid　multi-body　system,　a　geometric　error　model　has　been　established.　Based　on　this　model,　the　machining　error　can　be　quantitatively　described.　In　order　to　find　the　key　error　parameters　which　have　great　influence　on　machining　accuracy,　the　sensitivities　of　error　parameters　are　computed　by　taking　the　derivative　of　error　equation.　Calculation　and　example　show　that　the　key　factors　that　have　significant　influence　on　machine　tool　errors　can　be　identified　efficiently.